Vegetable seedlings need tons of light. If you don't have a sunny windowsill (5 hours or more), consider supplemental light. An inexpensive shop light using one cool white and one warm white bulb will work, IF you have the seedlings close enough to the bulbs, 6-10 inches. The link below shows how one person made a grow chamber, but the grow light works for me: http://suburbanvegetablegardening.com/poor-mans-grow-lighting/